1. Introduction
Introducing new generalized topological spaces and exploring their topological properties in various approaches has become a phenomenon in the development of mathematical sciences. Levine (see [1] ) in his paper “Semi-open Sets and Semi-continuity in Topological Spaces” generalized a topology by replacing open sets with semi-open sets and obtained some results. After that, different types of generalized open sets are introduced such as preopen, semi-preopen, etc. All these generalized sets have a common property which is closed under arbitrary union. In 1983, Mashhour et al. (see [2] ) considered all of these sets and defined a generalized space called supra topological space. In other words, the family of open sets is replaced with a larger one. So, the supra open sets are defined where the supra topological spaces are presented.
In 2008, Jassim (see [3] ) defined and studied compact, open cover, open sub cover concepts in supra topological spaces. In 2016 Al-Shami (see [4] ) introduced and investigated some notions in supra topological spaces such as almost supra compact, supra Lindelof, supra regular and supra normal spaces.
In 2018, Jassim et al. (see [5] ) introduced and defined a new class of topological transitive maps called topological semi-transitive, bi-supra transitive map by replacing open set in the definition of transitivity with semiopen and bisupra open sets (a subset A of a set X is called a bisupra-open set if
, where B is semiopen set and C is preopen set). As far as we know, the dynamics of supra topological space are not yet explored. So, motivated by this and the previously mentioned studies, we extend the study of supra topological space to a dynamical study. We define and introduce some supra chaos notions, i.e., supra transitive, supra totally transitive, supra mixing, supra l.e.o, and supra weakly blending in analogue to chaos notions of topological spaces and investigate the relations among these chaos notions on supra topological space and proved supra l.e.o implies supra mixing, supra totally transitive, and supra weakly blending. Also, we figure out their relations with the classical chaos notions and we showed that supra l.e.o, supra mixing, supra totally transitive, and supra weakly blending imply l.e.o, topologically mixing, totally transitive, and weakly blending, respectively.
2. Preliminaries
Definition 2.1. (See [6] ) A function
is said to be transitive if for any non-empty open subsets
, there exists
such that
.
Definition 2.2. (See [7] ) A function
is said to be totally transitive if
is transitive for all integers
.
Definition 2.3. (See [8] A function)
is said to be mixing if for any non-empty open subsets
, there exists
such that
, for all
.
Definition 2.4. (See [9] ) A function
is said to be locally everywhere onto or simply l.e.o if for every open subset
there exists a positive integer n such that
.
Definition 2.5. (See [10] ) A function
is said to be weakly blending if for any pair of non-empty open sets U and V in X, there is some
such that
, and strongly blending if, for any pair of non-empty open sets U and V in X, there is some
such that
contains a non-empty open subset.
Definition 2.6. (See [2] ) Let X be a set and
a family of subsets of X.
is said to be a supra topology on X, if the following axioms hold:
1. X and the empty set
are in
.
2. The union of an arbitrary family of members in
is also in
.
The members of
are called supra open sets, and the complement of a supra open set is called a supra closed set.
Definition 2.7. (See [2] ) Let
be a topological space, and let
be a supra topology on X. Then
is said to be a supra topology associated with
if
.
Definition 2.8. (See [11] ) Let
be a supra topological space and
. Then,
1. The supra closure of a set A is denoted by
and defined by
.
2. The supra interior of a set A is denoted by
and defined by
.
Theorem 2.9. (See [2] ) Let X be a set and
be a supra topology defined on X. Then,
1.
.
2.
.
3.
.
Proposition 2.10. (See [4] ) Let
be a supra topological space. Then for any subset A of X, the following holds;
1.
.
2.
.
3.
.
Definition 2.11. (See [2] ) Let
,
be topological spaces and
be a supra topology associated with
. A function
is said to be S-continuous if for each open set U in Y,
is
-supra open set in X.
Definition 2.12. (See [3] ) For a supra topology
, a supra open cover of a subset A of X is a collection
of supra open sets such that
.
Definition 2.13. (See [3] ) A supra topology
is said to be supra compact if every supra open cover of X has a finite subcover.
Theorem 2.14. (See [3] )
1. Every supra closed subspace of a supra compact space is supra compact.
2. If X is a finite supra topological space. Then X is supra compact.
3. Dynamics of Supra Topological Space
Throughout this paper, a pair
of a supra compact space X and S'-continuous
is said to be a supra dynamical system. A subset
is invariant if
. It is supra dense if for every supra open set U,
and nowhere supra dense if
. It is of supra second category, if A cannot be written as the countable union of subsets which are nowhere supra dense in X, i.e., if writing A as a union
implies that at least one subset
fails to be nowhere supra dense in X.
Definition 3.1. A supra topological space
is said to be supra separable if it has a supra dense subset which is countable.
Definition 3.2. A point
is called supra non-wandering point if for any supra neighbourhood U of x, there exists
such that
. The set of supra non-wandering points is denoted by
.
Proposition 3.3. For the set
, we have,
1.
is supra closed.
2.
is f-invariant.
3. If f is invertible, then
and
.
Proof.
(1) To see that
is supra closed, we show its complement is supra open. If
, then there exists a supra neighbourhood U of x such that
, for all
, and hence if
is any smaller supra neighbourhood of x, then all points
also do not belong to
. So, for every
, there exists
such that
and
. Thus
is a union of supra open sets in X. Therefore,
is supra closed.
(2) To show
is invariant, let
. Let V be a supra neighbourhood of
. Then
is a supra neighbourhood of x, and hence there exists some
such that
. The image of this intersection under f is contained in
, and hence
. Thus
.
(3) Let f be invertible and let
, then for every supra neighbourhood U of x there exists
such that
. The
image of this intersection is contained in
, which is nonempty, and hence
. Thus
. By the same argument, we can show that
, and then
. Thus
. Hence
. □
Definition 3.4. A supra dynamical system
is called supra minimal if the orbit of each point of X is supra dense in X.
Theorem 3.5 A dynamical system
is called supra minimal system if one of the three equivalent conditions hold:
1. The orbit of each point of X is supra dense in X,
2.
for each
,
3. For
and a nonempty supra open U in X, there exists
such that
.
Proof. If (1) holds, then by Definition 3.4 f is supra minimal. If (2) holds, then
, the orbit of each point
is supra dense in X. Therefore f is supra minimal. If (3) holds, then
, the orbit of each point
is supra dense in X. Therefore f is supra minimal. □
Theorem 3.6. For a supra dynamical system
, the following are equivalent:
1.
is supra minimal,
2. If F is a supra closed subset of X with
, then
or
,
3. For a nonempty supra open set U of X,
.
Proof.
(i) (1)
(2): Let f be a supra minimal map, and let F be a supra closed subset of X with
. If
, let
, since F is a supra closed subset of X, then
, hence
. But by (2) of Theorem 3.5 we have
. Therefore
.
(ii) (2)
(3): Let U be a nonempty supra open set of X. Let
. Since U is a nonempty set then
. Since f is S'-continuous and U is a nonempty supra open set, then B is a supra closed set and
, so B must be empty. Therefore
.
(iii) (3)
(1): Let U be any nonempty supra open set of X, and let
. Since
, then
. Hence
for some
, i.e., the orbit of every point x in X is supra dense in X. Therefore,
is supra minimal. □
Definition 3.7. A supra dynamical system
is said to be supra transitive if for any non-empty supra open subsets
, there exists
such that
.
Proposition 3.8. A function
is supra transitive if and only if for every nonempty supra open set U in X,
is supra dense in X.
Proof. Let f be a supra transitive function, and let U be a nonempty supra open set in X. Suppose that
is not supra dense in X, then there exists a supra open set V such that
. This implies that
for all
, which is a contradiction since f is a supra transitive. Conversely, Let U and V be two nonempty supra open sets in X. Since
is supra dense in X, then for every supra open set V we have
. Hence there exist an integer
such that
. Therefore f is supra transitive. □
Proposition 3.9. Let
be a supra dynamical space. If there exists a supra dense orbit, then f is supra transitive.
Proof. Let U and V be two nonempty supra open sets in X, and let
such that the set
is supra dense. Since
is supra dense, there exists
such that
. Since
is supra dense, then
is also supra dense. Hence there exists m such that
. Therefore
, and then
. So f is topological supra transitive. □
Proposition 3.10. Let
be a supra dynamical space. If X is supra separable and of supra second category, then supra transitivity of f implies that f has supra dense orbit.
Proof. Let X be a supra separable and of supra second category. Let
be a countable supra base for X, and suppose that f has no supra dense orbit, then for each
there exists
such that
for every
. Let
, then U is a supra open and meet every supra open set since f is supra transitive. Let
,
then
is a supra closed set since it is a complement of supra open set and nowhere supra dense. However,
is a countable union of nowhere supra dense sets which contradicts the fact that X is of supra second category. Therefore f has supra dense orbit. □
Proposition 3.11. Let
be a supra dynamical system. If f is supra transitive then X does not contain two disjoint supra open invariant subsets of X.
Proof. Let f be a supra transitive map, and let U and V be two disjoint, supra open, invariant subsets of X. Since U is invariant then
, and hence
, which is a contradiction since f is supra transitive. Therefore X does not contain two disjoint supra open invariant subsets of X. □
Proposition 3.12. Let
be a supra dynamical system. If f is supra transitive then X is not a union of two proper supra closed invariant subsets of X.
Proof. Let f be a supra transitive map, then by Proposition 3.11, X does not contain two disjoint, supra open, invariant subsets. Suppose that B1 and B2 are two proper, supra closed, invariant subsets such that
. This means that we can write
where B1 and B2 are nonempty proper supra closed, invariant subsets if and only if we can find nonempty proper supra closed, invariant subsets B1 and B2 such that
. Since B1 and B2 are supra closed subsets, then
and
are two disjoint, supra open, invariant subsets of X, which is a contradiction since X does not contain two disjoint, supra open, invariant subsets. Therefore, X is not a union of two proper supra closed invariant subsets of X. □
Definition 3.13. A supra dynamical system
is said to be supra totally transitive if
is supra transitive for all integers
.
Definition 3.14. A supra dynamical system
is said to be supra mixing if whenever U and V are nonempty supra open subsets of X, there exists an
such that
, for all
.
Definition 3.15. A supra dynamical system
is said to be supra locally everywhere onto or simply supra l.e.o if for every supra open subset
there exists a positive integer n such that
.
Definition 3.16. A supra dynamical system
is said to be supra weakly blending if for any pair of non-empty supra open sets U and V in X, there is some
such that
.
Next, we show the relation between each supra chaos notion and its analogue in topological space.
Proposition 3.17 Let
be a supra dynamical system. If f is supra l.e.o, then it is l.e.o
Proof. Let U be any nonempty open subset of X. Since every open set is supra open set, and since f is supra l.e.o, then there exists an integer
such that
. Therefore f is l.e.o □
Proposition 3.18. Let
be a supra dynamical system. Then
1. If f is supra totally transitive, then it is totally transitive.
2. If f is supra mixing, then it is mixing.
3. If f is supra weakly blending, then it is weakly blending.
Proof. By the same argument in the proof of Proposition 3.17. □
After showing the relation between each supra chaos notion and its analogue in topological space, we will show the relation between the supra chaos notions, i.e., supra l.e.o, supra topologically mixing, supra totally transitive, and supra weakly blending.
Proposition 3.19. Let
be a supra dynamical system. If
is a supra l.e.o, then it is supra transitive.
Proof. Let U and V be any nonempty supra open subsets of X. Since f is supra l.e.o, then for any supra open U, there exits integer
such that
. So for any supra open V of X, we have
, for some
. Therefore f is supra transitive. □
Proposition 3.20. Let
be a supra dynamical system. If
is a supra l.e.o, then it is supra totally transitive.
Proof. Let
be any two nonempty supra open sets in X. Since f is supra l.e.o, then for every supra open set U there exists a positive integer n such that
. Let
be any integer, then we have
and so
.
Hence f is supra totally transitive. □
Proposition 3.21. Let
be a supra dynamical system. If
is a supra l.e.o, then it is supra mixing.
Proof. Let
be any two nonempty supra open sets in X. Since f is supra l.e.o then for every supra open set U there exists a positive integer n such that
, and then
. So we can choose
such that
for every
. Hence f is supra mixing. □
Proposition 3.22. Let
be a supra dynamical system. If
is a supra l.e.o, then it is supra weakly blending.
Proof. Let
be any two nonempty supra open sets in X. Since f is supra l.e.o, then there exists
such that
Without lose of generality, let
. Then
So
Hence f is supra weakly blending. □
4. Conclusion
In this paper, we introduced some concepts of supra chaos notions, i.e., supra transitive, supra totally transitive, supra mixing, supra l.e.o, and supra weakly blending. Firstly, we studied the properties of supra transitive map and after that we figured out the relation between the classical chaos notions and supra chaos notions, and proved that supra l.e.o, supra mixing, supra totally transitive, and supra weakly blending imply l.e.o, topologically mixing, totally transitive, and weakly blending, respectively. Secondly, we showed that supra l.e.o implies supra mixing, supra totally transitive, and supra weakly blending.
Acknowledgements
The authors would like to thank the National University College of Technology for the financial funding.